Hydraulic method and apparatus



Dec. 10, 1968 G. L.. oMoN HYDRAULIC METHOD AND APPARATUS Filed Mays, 19e? United States Patent O 3,415,053 HYDRAULIC METHOD AND APPARATUS Geile L. Omon, Wauwatosa, Wis., assignor to J. I. Case Company, Racine, Wis. Filed May 5, 1967, Ser. No. 636,401 6 Claims. (Cl. 60-14) ABSTRACT F THE DISCLOSURE An internal combustion engine powered vehicle having a hydraulic system for supplying a hydraulic liquid under relatively high pressure to motor elements under the control of a valve. The entire hydraulic system is maintained at a super-atmospheric pressure by drawing ltered air at the carburator inlet to the combustion engine, continuously deliverying the withdrawn air at a predetermined pressure to maintain a chamber at a predetermined pressure level with means for interconnecting the chamber and the hydraulic system to continuously maintain the hydraulic system at the predetermined superatmospheric pressure.

Background of the invention The present invention relates generally to a hydraulic method and apparatus and more particularly to an irnproved hydraulic system for continuously supplying superatmospheric liquid to a system pump by regulating the flow of a pressurized fluid into the hydraulic system to thereby maintain the liquid in the hydraulic system at a predetermined super-atmospheric pressure.

In the operation of various types of industrial equipment, it has been conventional to provide hydraulically actuated motor elements, such as fluid cylinders, for controlling the movement or actuation of various components associated with a vehicle. Conventionally these vehicles include a continuous hydraulic system for conveniently providing hydraulic liquid from a reservoir to the motor elements to actuate the motor elements and also return the liquid to the reservoir for subsequent reuse in the system. Since such vehicles normally operate in a surrounding atmosphere where dust and air-borne solids are necessarily present, contaminants readily become intermixed with the liquid, such as oil, in thc. reservoir and the entire system shortly becomes contaminated.

Various systems have been proposed for limiting the direct communication between the reservoir and the atmosphere by utilizing elaborate ilters or cleaners to remove the dust or air-borne solids from the air entering into the reservoir from the atmosphere. However, in such systems it is virtually impossible to provide contaminant free air to the reservoir and the filters must continuously be replaced or -cleaned in order for the system to be even partially satisfactory. y

One other type of system which has been proposed is to provide a closed pressurized hydraulic system with means for intermittently supplying clean, pressurized hydraulic liquid from an atmospheric chamber into the superatmospheric closed hydraulic system. Such a system is disclosed by Harold A. Lehmann in Patent No. 3,222,866 and by R. I. Miller in Patent No. 3,222,865.

Summary of the invention Generally speaking, the present invention includes a method of and apparatus for maintaining a closed hydraulic fluid system at superatmospheric pressure by drawing filter air from an air stream directed to a combustion engine, compressing the air drawn from the air stream and intermittently feeding the pressured air to the hydraulic fluid reservoir of the closed system.

FCice The primary object of the present invention is to provide an improved method of and apparatus for maintaining it closed hydraulic system at a predetermined pressure evel.

Another important object is the provision of improved means for maintaining the liquid in a closed hydraulic system at super-atmospheric pressure.

Still another object is to provide an improved method of intermittently supplying a pressurized uid to a closed hydraulic system to maintain the hydraulic liquid in the system at a predetermined pressure level.

A still further object is the provision of a novel method and apparatus for continuously suppling contaminant free hydraulic liquid to the pump of a hydraulic system.

Other objects and features of the invention will become apparent when considered in conjunction with the following specification and the accompanying drawings.

In the drawings The single figure of the drawings is a schematic representation of a hydraulic system of conventional type provided with means of the present invention for maintaining the liquid in the system at a predetermined pressure.

In the specz'jcaton:

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

Reference numeral 10 of the ligure indicates generally a hydraulic system of the type conventionally utilized in industrial vehicles, such as a self-propelled loader. For example, the system is readily adapted to be used with a power operated vehicle, such as disclosed in Patent No. 3,220,580, issued to E. B. Long and assigned to the assignee of the present application.

The hydraulic system 10 includes a geartype system pump 12 delivering pressurized liquid, such as oil, through a conduit 14 to a plural-spool control valve, indicated generally at 16. The control valve is illustratively `shown as including first and second valve spools 18 and 20 with the spool 18 capable of being actuated to deliver pressured liquid to a first pair of cylinders 22 through conduits 24 or 26. The second spool 20, when actuated, delivers liquid under pressure to a second pair of cylinders 28 through conduits 30 or 32.

In accordance with the teachings of the above mentioned patents, pressurized liquid is continuously supplied from a main tank or pressurized reservoir 34 through conduit 36 to the pump 12. The pressurized liquid is further pressurized by the pump 12 and passes through the control valve 16 to actuate the respective cylinders 22 or 28. The used hydraulic fluid, i.e. return fluid from the cylinders 22, 28 or the uid merely passed through the valve 16 from the constant displacement pump 12, is returned through line 38 to the reservoir 34 to be reused for subsequent liquid to the inlet of the pump 12.

According to one aspect of the invention, the pressurized liquid entering the conduit 36 interconnecting the inlet of the pump 12 with the oil reservoir 34 is filtered at the outlet of the reservoir to eliminate any contaminants which may have entered the reservoir 34. For this purpose, the outlet opening 39 of the reservoir 34 is sealed from the main chamber 35 by a plate 40 secured to the end wall of the reservoir 34, as by welding. The plate 40 is provided with a plurality of openings each of which re- 3 ceives the end portion of a perforated tube 42 forming part of the lilter 44.

During normal operation, oil passes through the filter wherein any contaminants in the oil are removed and is delivered through the perforated tube to the outlet of the reservoir 34. A bypass valve 46 normally closes the opposite end of the tube 42. However, if the filter for any 'reason becomes clogged or, for any other reason, the pressure drop across the lter is greater than a predetermined amount, for example 4 p.s.i., the check valve or bypass valve 46 will open to provide a direct bypass through the center part of the lter and place the opening 39 in direct communication with the chamber 35 of the reservoir 34.

According to a further aspect of the invention, means are provided for maintaining the liquid in the reservoir at super-atmospheric pressure which is substantially less than the output pressure of the system pump 12. This means includes a second or uid reservoir 50 communicating with the chamber 35 of the first reservoir 34 through conduits 52 and 54 with a regulator valve 56 interposed therebetween. The regulator valve is in open communication with the atmosphere through a third conduit 58.

Fluid supply means are connected to the reservoi-r 50 for delivering pressurized uid, such as air, to maintain the pressure in the second reservoir greater than the pressure in the first reservoir. In the illustrated embodiment, the second reservoir 50 is maintained at a predetermined pressure level through conventional elements forming a part of the self-propelled vehicle. Thus, a vehicle of the above type includes an internal combustion engine 60 having a carburetor (not shown) with communicating means or a conduit 62 connected in liuid flow relation to the housing of an air cleaner 64 that is in open communication with the atmosphere. The air from the atmosphere is drawn yinto the air cleaner wherein it is ltered to remove any contaminants, and thereafter passes through the conduits 62 into the carburetor of the internal combustion engine.

According to the invention, a conduit 66 is connected to the conduit 62 interconnecting the air cleaner 64 with the carburetor. The opposite end of the conduit is in communication with an air compressor 68 that maintains the main air reservoir 70 at a predetemined pressure level. The main air reservoir conventionally supplies pressurized air for operating components of the vehicle, such as the air brakes or born.

A fluid conduit 72 interconnects the main air reservoir 70 with the uid reservoir 50 with a pressure protection 'valve 74 interposed in the conduit 72 to maintain a predetermined pressure ditferential between the respective reservoirs.

The pressure protection valve 74 will operate to respond to iiow in relation to pressure in the conduit and also operates within certain pressure limits. Thus, the valve will close when the pressure in the conduit 72 between reservoir 70 and valve 74 falls below a predetermined value to prevent other air pressure operated components, such as a-ir brakes (not shown), connected to conduit 72 from operating properly.

Suitable gages 76, 78 may be connected to the lines 72 and 54 to provide a visual indication of the respective pressures in the fluid system. Also, a low pressure warning device 82 may be provided in the conduit 72 to indicate that the pressure -in the main reservoir 70 has fallen below a minimum level.

The air compressor 68 is also in communication with the outlet of the main air reservoir 70 through conduit 84 having a sensing mechanism 85 to intermittently actuate the compressor whenever the pressure in the reservoir falls below a predetermined desired level.

The pressure regulator 56 is of the commercially available type and includes means for providing infinite incremental settings and locking means for maintaining the pressure in conduit 54 at a predetermined pressure above atmospheric pressure which is sensed through conduit 58. Therefore, after the regulator has been set at a predetermined value, such as l2 p.s.i., when the pressure in the reservoir or oil tank chamber 35 falls below a predetermined level, pressurized air will pass from conduit 52 through the regulator and conduit 54 into the chamber 35. Likewise, if the pressure in the chamber 35 exceeds the predetermined pressure level, the conduit 54 will be placed in communication with the atmosphere through conduit 58 to lower the pressure to the predetermined level.

To insure that no air enters into the conduits of the hydraulic system during normal operation of the system, the return conduit 38 leading from the control valve 16 includes an extension 90 disposed a considerable distance below the oil level 92 within the chamber 35 and the lower end thereof is provided with a screen 94 to remove any large particles of dirt which may have been interjected into the oil while iiowing through the system. Thus a closed hydraulic liquid flow path is formed between conduits 36 and 38. Furthermore, suitable filtering mechanism, such as a strainer 96 may be connected to the opening of the reservoir communicating with the air inlet conduit 54. Of course, suitable drain valves 98 may be provided for the respective reservoirs to drain the reservoirs whenever desired.

A hand regulated valve is interposed in the conduit 52 between the reservoir 50 and the pressure regulator 56 so that the hydraulic circuit may be isolated from the fluid system. For safety reasons, it is important that the valve 80 is located on the inlet side of the regulator. Thus, if for any reason the operator neglects to open the valve after servicing the system, the outlet conduit is still in communication with the pressure reservoir 34. This will prevent overpressurization of the hydraulic reservoir 34.

The operation of the System is readily apparent from the above mentioned description. A sufiicient amount of oil is introduced into the system to meet all of the demands of the various motor elements. The engine 60 is ignited and the continuous demands of the internal combustion engine will produce a flowing stream of air through the conduit 62 into the engine.

The air compressor 68 is actuated through the sensing mechanism to draw a certain amount of clean, filtered air through conduit 66 and deliver compressed air through conduit 69 and check valve '71 to the main air reservoir. The pressurized air will enter the main reservoir 70 and will pass through conduit 72 and valve 74 into the uid reservoir 50 and into the various other components of the system.

Once the pressure level in the respective reservoirs 34, 50 and 70 is reached, the operation of air compressor 68 will be temporarily discontinued through the mechanism 85. Thereafter, the chamber 35 will be maintained at a predetermined pressure level to constantly supply pressurized liquid through the filters 44 and conduit 36 to the inlet of the pump 12 or bypassing the filters and passing directly from the chamber into the conduit 36. If the pressure level in the reservoir 34 should fluctuate the pressure regulator 56 will automatically return the pressure to the predetermined level.

Thus, it will readily be apparent that the present invention provides a unique method and apparatus for continuously supplying super-atmospheric liquids to the pump of a continuous hydraulic circuit by utilizing many of the conventional components of a self-propelled vehicle.

While a preferred embodiment of the invention has been shown and described, it will be understood that various changes and modifications may be made without departing from the spirit of the invention as defined by the following claims.

I claim:

1. In a method of supplying super-atmospheric hydraulic liquid to the system pump of a closed hydraulic system and wherein the hydraulic system is combined with a vehicle having a combustion engine using a flowing stream of air which is filtered and supplied to the engine to produce a gaseous fuel mixture and the hydraulic system includes a reservoir from which hydraulic liquid is circulated through the system and returned to the reservoir, the improvement comprising:

(l) confining a pressurized fluid in a second reservoir (2) providing a liuid passage between the reservoirs (3) diverting a portion of the filtered fiowing stream of air (4) compressing the diverted air (5) delivering the compressed air to the second reservoir as said pressurized fluid, and

(6) regulating the flow of the pressurized liuid between the reservoirs to maintain the hydraulic liquid in the first reservoir at predetermined super-atmospheric pressure.

2. A method as defined in claim 1, wherein the fiow of fiuid between the reservoirs is regulated in response to the pressure level in the first reservoir.

3. A method as defined in claim 1, and wherein the liquid passing from the first reservoir to the system pump is passed through a filter, the further improved step of bypassing the filter when the pressure drop across the filter is greater than a predetermined amount to prevent pump cavitation.

4. In a closed hydraulic system in combination with a combustion engine having a carburetor with communicating means connected in fluid fiow relation to an air filter housing having an air inlet opening and wherein the system supplies hydraulic liquid from a reservoir to a motor element through a system pump under relatively high pressure and the control of a valve element, with means for maintaining the liquid in the reservoir at superatmospheric pressure substantially less than the output pressure of said system pump, the improvement comprising a second reservoir, first conduit means interconnecting said irst and second reservoirs, second conduit means interconnecting said communicating means and said second reservoir for delivering pressurized fluid to said second reservoir, means in said second conduit means for maintaining the pressure in the second reservoir greater than the pressure in the first reservoir, and regulator means in said first conduit means for controlling the fiow of pressurized fiuid in said rst conduit means between said reservoirs to maintain the pressure in the first reservoir at a predetermined level.

5. A hydraulic system as defined in claim 4, in which said regulator means includes a valve communicating with the atmosphere to maintain the pressure in first reservoir at a predetermined level above atmospheric pressure.

6. A hydraulic system as defined in claim 4, in which said second conduit means includes means for continuously maintaining the fluid in the second reservoir at a pressure higher than the pressure in the first reservoir.

References Cited4 UNITED STATES PATENTS 2,339,086 1/ 1944 Makarof 60-51 2,575,308 11/1951 White 60-51 2,665,551 1/1954 Chenault 60--51 2,846,139 8/1958 Blount et al. 103-220 X 3,116,596 l/1964 Boehme et al. --30 3,222,866 12/1965 Lehmann 60-52 3,235,085 2/1966 Humbert 210-13() EDGAR W. GEOGHEGAN, Primary Examiner. I

CARROLL B. DORITY, Assistant Examiner.

U.S. Cl. X.R. 60-51 

